There are a variety of apparatus available for styling hair. One form of apparatus is known as a straightener which employs plates that are heatable. To style, hair is clamped between the plates and heated above a transition temperature where it becomes mouldable. Depending on the type, thickness, condition and quantity of hair, the transition temperature may be in the range of 160-200° C.
A hair styling apparatus can be employed to straighten, curl and/or crimp hair.
A hair styling apparatus for straightening hair is commonly referred to as a “straightening iron” or “hair straightener”. FIG. 1a depicts an example of a typical hair straightener 1. The hair straightener 1 includes first and second arms 4a, 4b each comprising a heatable plate 6a, 6b coupled to heaters (not shown) in thermal contact with the heatable plates. The heatable plates are substantially flat and are arranged on the inside surfaces of the arms in an opposing formation. During the straightening process, a squeezing force is applied to the arms so that they rotate about pivot 2 to clamp hair between the hot heatable plates. The hair is then pulled under tension through the plates so as to mould it into a straightened form. The hair straightener may also be used to curl hair by rotating the hair straightener 180° towards the head prior to pulling the hair through the hot heatable plates.
A hair styling apparatus for crimping hair is commonly referred to as a “crimping iron”. FIG. 1b depicts an example of a typical crimping iron 10. The crimping iron includes first and second arms 14a, 14b coupled about hinge 12 to allow the arms to open and close. Each arm comprises a heatable plate 16a, 16b coupled to heaters (not shown) in thermal contact with the heatable plates. The heating plates have a saw tooth (corrugated, ribbed) surface and are arranged on the inside surfaces of the arms in an opposing formation. During the crimping process, the hair is clamped between the hot heatable plates until it is moulded into a crimped shape.
More effective heating, and consequently styling, can be achieved by applying heat to both sides of a quantity of hair. This is why many styling apparatus provide heatable plates on both arms.
One downside of this opposing arm arrangement is that squeezing pressure exerted on the arms can lead to undesired play in movement of the arms, including unintended sideways movement of the arms, known as yaw, and also roll of the arms. An example of the yaw problem is shown in FIGS. 2a and 2b. In FIG. 2a, it can be seen on hair styling apparatus 3 that arm 7, which rotates about pivot 5 relative to arm 9 has become offset as a result of an applied pressure by the user. (It will be appreciated that the offset/yaw has been overemphasised in FIG. 2a for illustrative purposes.) FIG. 2b is a schematic illustration of the apparatus of FIG. 2a showing the bending axes. The correct bending axis b is the dotted line passing along the central short axis of the apparatus. When there is yaw, the bending axis is rotated about an angle φ to become axis b′.
In the process of clamping hair between the plates, hair may be pushed off the end of the heating plates as the arms are clamped over the hair, meaning the arms need to be released and the quantity of hair reclamped. Another disadvantage of yaw is that it may reduce the surface area in contact with the hair and hence the effectiveness of the styler. Any undesired play in the arm-pivot coupling can be further exaggerated if a user squeezes especially hard to prevent hair escaping. Yaw is particularly problematic when using a hair straightener to create curls by wrapping the hair at least partially around the styler.
The applicant has therefore recognised that radically different approaches are needed to overcome these problems.